Concentration of sodium nitrate or potassium nitrate.



H. S. COE.

CONCENTRATION 0F soDluM NITRATE 0R PoTAsslUM NITRATE.

APPLICMION FILED SEPT-29.1917.

Patented Jan. 28. 1919.

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ing to be a full, clear, and exact description of the invention, such as Will enable. others un n srfrns PATENT onirica..

HARRISON STREETER COE, OF IVIOUND CITY, KANSAS, ASSIGNOR'TO THE DORR COMPANY, A CORPORATION OF DELAWARE.

CONCENTRATION OF SODIUM NITRATE OR POTASSIUM NITRATE.

Specification of Letters Patent.

Patented Jan. .28, 1919.

vApplication led Septemberl29, 1917. Serial No. 193,903.

To all whom t may concern Be it known that I, HARRISON STREETER Con,.residing at Mound City, in the county of Linn, State of Kansas, have invented certain new land useful Improvements in lConcentration of Sodium Nitrate or Potassium Nitrate; and I do hereby declare the followskilledin the art to Which it appertains to make and use the same.

This invention relates fto the production of niter, either sodium nitrate or potassium nitrate, from niter-bearing earthy and crystalline material or from niter-bearing residues or by-products of industrial plants.

It has for an object the securing of a more complete recoveryof niter from the ravv material and to do this at low expense by avoiding troublesome heating or extensive evapo ration.

Two methods are in use for obtaining niter of commercial purity from natural niter-bearing material or fromniterbearing residues from industrial plants. The ordinary method consists in treating the niter-- bearing material in counter current WithI This solution is drained from the undissolvedl residuevof the material and -cooled, thus crystallizlng out niter of a commercial grade.l The evaporation inciden.I to theu heatlng aids materially in strengthening the solution and in disposing of the Water used The solid materials remaining behind when the concentrated niter liquor 1s drained .in nally Washing the residues.

` ofi' are still Wet with the rich liquor and so hold a considerable quantity of the original niter content. Washing in leaching vats may be resorted to, but on Washing with Water thepreviously precipitated sodium chlorid and the like go into solution and'troublesome and expensive evaporation of the solution must .bef resorted to, and besides, thel solution vobtained by Washing lis so lean in I"niter and so rich in sodium chlorld and similar materials that the operation is not economical. Perfect washingl is not practical and under. any circumstances much niter- :bearing solution is lost in the residue.

The second method consists in leaching the ore or other niter-bearing material With a more dilute niter solution than the hot solution above described and later concentrating by evaporation until by increase in temperature and in niter content the sodium chlorid and like impurities are crystallized will crystallize out along With the niter` .when the liquor is cooled, thereby rendering the crystallized product of a grade undesirf vable for commercial purposes.

By the use of the present invention I am able to avoid the troublesome high heating of0 the first process above outlined andthe extensive and expensive evaporation incident to the second method above referred to.

I have found that the `niter-bearing material such as niter ore or niter-bearing industrial residues may be treated with an aqueous solution of niter and caused to give up substantially its full niter content and I am able to do this in such a Way that evapora: tion of relatively large volumes of Water is avoided.lz In fact by judicious handling of the process the amount of Water constantly being added to the system need not appreciably exceed that discharged with the Wet ore residues plus the amount naturally evapo-,

ratedduring thetreatment for solution of niter. The temperature at Which the niterbearing material is treated is considerably below the temperature at which most of the sodiumfhlorid is thrown out of solution and consequently on completion of the treatment of'the ore With the aqueous solution of so# dium nitrate the resulting liquor Will, on chilling or cooling, yield by crystallization, an impure nitrate. In this crystallized product I have substantially all of the niter content of the original material under treat-l this impure crystallized nitrate consists in mixing it with a proper proportion of solution which is saturated .with niter and 1m- Apurities either when cool or when moderately hot and then digesting the mixture at a high temperature, whereupon the niter present will dissolve and the sodium chlorid and some other impurities will remain undissolved and part of the sodium chlorid and certain other impurities initially present in the solution will be deposited from the solution as the niter is dissolved. The substances |which have failed to go into solution or which have been precipitated out may be. allowed t0 settle' outv and subsequently freed from niter solution by a centrifugal drying or by liltration and later can be re-'treated together with fresh niter-bearing material .to remove the last of the niter content.

The solution thus produced 'by digesting the impure crystallized nitrate with the rich solution of impure nitrate may be made to contain such a niter content that upon chill- `ing. or slow cooling there will crystallize out a commercially pure nitrate. Such a solu tion will be similar in every way to the solutions of full crystallizing strength sought by the two` processes now in use, as above outlined, and yet will have been obtained without the loss of nitrate in the residue now incident to the `hot digesting method and without the expensive step of concentration by evaporation which is inherent in the second method. Further, looking at the process from a different angle it will be seen that the invention contemplates the digestion of an impure niter with an impure sof lution of niter, with the production of two important results, viz., the addition of niter to the solution and the precipitation of impurities therefrom.

The details of the operationy by which substantially the entire niter Vcontent of the original material is caused to go into solution and the subsequent steps whereby that impuresolution is 4freed from much ofits sodium chlorid and other impurities to yield a solution from which commercial niter can be crystallized are set forth hereinafter more in detail in connection with an 4'apparatus vindicated by the accompanying drawing.

In 'the drawing the figure illustrates diagrammatically and with parts in section aV system whereby the proposed process can b e The process' claimed may be carried out with apparatus varying radically from that indicated inthe drawing, but the drawing shows one satisfactory arrangement of elements. The details of these elements and.0 their relation to one anotherare set forth,A

- so far as they are relevant, in the following' description of the process as a whole. i,

In the-"process the .niter-bearing material is first crushed ina crushing machine of any l particular! type illustrated conventionally on the drawing, and designated by the numeral 1. falls intoa storage bin 2 and from the store age bin the material is drawn and mixed with hot niter solution from the tank 16,

and the mixture is charged into a ball'mill.

3. This solution is obtained in the process and is, when cold, saturated with niter and with sodium chlorid. In the ball mill 3 the material and solution become thoroughly ground to form a slime or slurry which is From the crusher uthe material led off by pipe 3 into tank 4 where it bey through pipe 5 and a portion of it isY conducted to the cooling spray 7 The liquid falling from the spray 7 through the atmosphere becomes materially cooled and somewhat more concentrated by evaporation, and on being collected in crystallizer 6, "I

crystallizes out a considerable proportion of the dissolved solids, which solids are the impure nitrate hereafterreferred to.

lution from crystallizer 6 is drawn off through pipe 6 to the main 17 and returned to tank 16. 'lhe solids from crystallizer 6, which solids are impure nitrate crystals, are conveyed to digester 10 for further treatment.

The portion of the solution from the filterY 5 not conveyed to spray 7 is led into digester 8 where it is mixed with solids from heated settler 11. These solids are composed of the impure nitrate from crystallizer 6 which have been digested with a very-strong nitrate solution and contain some nitrate and "most vof the impurities from the .final solution of nitrate. Digester 8 is heated by means of a steam coil and the' solution produced by the digestion is a moderately strong solution of ,nitrate containing some sodium chlorid. The mixture of solids and liquid is transferred to settler 9, and sodium chlorid and other impurities separated out and are drawn olil into centrifugal machine 12. The solution from the settler 9 is conveyed to digester 10 where" it is mixed with impure nitrate from crystallizer 6 and partly digested under heat from the vsteam co'il therein. The mixture of solids and liquids from digester 10 having a temperature'of Afrom 100 't`opl20o` C. is conveyed without The socooling to settler 11, where the partly` di,n

-gestion in 10 completes 'the saturationv with tion.

nitrate and substantially completes the elimination of the sodium chlorid from solution. The solution from 11 is conveyed to the cooling spray l5 which causes the solution to be cooled and concentrated by evapora- Crystals of commercially pure nitrate are deposited in crystallizer 13, which crystals are drawn oii', centrifuged and packed as a final product, and from crystallizer 13 and centrifugal machine 14 is conveyed the mother liquor to main 17 and thence to tank 16. vThe solution in tank 16 is thus seen to be a nitrate solution Which is saturated at ordinary temperatures with both niter and sodium chlorid, and which, when heated, is ycapable of taking up more nitrate. This solution is heated to from 50 to C. by means of the steam coil in tank 16 and returned to the process through the ball mill 3, as shown. The solid material conveyed from the settler 9 into centrifugal machine 12 is composed largely of sodium chlorid, but may contain some nitrate both undissolved and in the solution remaining therein. The liquid separated by the machine is drawn 0E through pipe 12 into pipe 6 and thence to digester l0. yThe solids after having been treated in the machine are returned to tank 4, Where they are mixed with the fresh, raw material and the solution coming from ball mill 3.

It is to be understood that the installation of apparatus includes the supply of any valves, pumps and conveyers necessary to control or cause the transfer of liquids or solids or mixtures thereof to and through and out of the system. It is also to be understood that by properly regulating .the supply of material the process may be made continuous, or substantially so.

In explanation of the process the following points are stated.

The solution in tank 16 is, when colol, a saturated solution 0f nitrate and it also contains some sodium chlorid. This solution when heated to from 50 to 70 C. becomes capable of dissolving considerable nitrate, but very little more sodium chlorid. The quantity of sodium chlorid in solution will be the same each time the solution goes to spray 7 and is determined by the temperature and the percentage of nitrate contained, as these conditions limit the power of the solution t0 dissolve sodium chlorid. Any excess of sodium chlorid is accordingly discharged from the system along with the insoluble portion of the ore.

It will be seen therefore that I am operating with a solution that is at all times substantially or completely saturated with common'salt, but capable of taking up and depositing nitrate with the corresponding changes in temperature.

What I claim is:

1. The process of recovering niter from niter-bearing material, Which comprises dissolving the niter from the said material by treatment at a temperature from about 50 C. to about 70O C. with a solution which is saturated when cold or moderately Warm with niter and also With'soluble impurities of the niter-bearing material, and cooling the solution so produced to obtain an impure nitrate; substantially as described.

2. The process of recovering niter from niter-bearing material, which comprises dissolving the niter from the said material by treatment with a heated solution which is saturated when cold or moderately warm with niter and also with soluble impurities of the niter-bearing material, and digesting at a higher temperature the solution so produced with impure nitrate so as to add to the solution a further proportion of nitrate; substantially as described.

3. The process of recovering niter from niter-bearing material, which comprises dissolving the niter from the said material by treatment with a heated solution Which 1s saturated when cold or moderately Warm with niter and also with soluble impurities of the niter-bearing material, digesting at a higher temperature the solution so produced with impure nitrate so as to add to the solution a further proportion of nitrate, cooling the latter solution with the solids therein suspended to deposit. the solid maf terial containing most of the impurities and returning the latterl to the first stage of the process; substantially as described.

4. The process of recovering niter from niter-bearing material, which comprises dissolving the niter from the said material by treatment with a heated solution which is saturated when cold or moderately Warm with niter and also with soluble impurities of the niter-bearing material, digesting at a higher temperature the'solution so produced with impure nitrate so as to add to the solution a further proportion ofnitrate, causing the latter solution with the solids therein suspended to deposit the solid mafterial contalning most of the impurities and returning the latter to the first stage of the process, and digesting with the mother liquor from the last step and at a temperature of 100 to 120 C. impure nitrate so as to form a saturated solution of nitrate, then separating and cooling this solution to crystallize out commercially pure nitrate; substantially as described.

5. The process of recovering niter from niter-'bearing' material, which comprises the steps of crushing the ore, grinding the crushed ore in the presence of a heated solution of niter, separating the liquids and solids While warm, crystallizing impure niter from a portion of said solution digesting with the remaining ortion of the solution impure niter containing solids from a subsequent step, cooling the mixture to cause crystallization of the dissolved salts, separating the solution therefrom, digesting Withrthis solution at a higher temperature the impure niter crystals first obtained, separating the solids, cooling the solution to crystallize out commercially pure nitrate and returning the mother liquor to the first stage of the process; substantially as described. I

6. rlhe process, which comprises chilling a Warm nearly saturated solution containing nitrate and'l impurities to produce impure crystals'of niter and digesting these with an under-saturated solution of niter at ahigher temperature, settling out the undissolved material and crystallizing niter from the solution; substantially as described.

7. rlhe process, which comprises passing a body of liquid which is saturated When cold With sodium nitrate and sodium chlorid through a niter-bearing material While maintaining a temperature of 50 to 20 C., dividing the resultant solution, cooling one part thereof to crystallize impure niter, digesting this impure niter in a plurality of steps with the other part of the said solution on the counter-current principle and at successively higher temperatures, crystallizing the niter from the so-produced solution and returningthe mother liquid to the first step for the treatment of further ravvr material; substantially as described.

8. rlhe process," which comprises passing a body of/liquid which is saturated When cold with sodium nitrate and sodium chlorid through a niter-bearing material While maintaining a temperature of 50 to 70o C., Washing the undissolved material with an amount of Water substantially equal to that lost in the process and adding the Washings to the solution, dividing the resultant solution, cooling one part thereof to crystallize impure niter, digesting this impure niter in a plurality of steps with the other part cf the said-solution on the counter-current principle and at successively higher temperatures,

high temperature with impure niter crystals rasate@ whereby further niter is added to and impurities are precipitated from the solution; substantially as described. c

l0. The process of recovering niter from niter-bearing material, which comprises dissolving the niter lfrom said material under such conditions that the resulting solution contains in addition to the niter a relatively large amount of impurities, cooling said resulting solution to obtain impure crystals of niter, and digesting at a high` treatment at a temperature from about 50 (i to about 70 C. with a solution which is saturated when cold .or moderately Warm with niter and with soluble impurities of the niter-bearing material, cooling the solu.- tion so produced to obtain impureA niter crystals, digesting said impure nitercrystals at a' temperature from about 100O C. to about i200 C. with a solution Which, when cool or moderately Warm, is saturated with niter and impurities, and crystallizing niter from the solution produced by the digesting operation; substantially as described.

12. rlhe process of recovering niter from niter-bearing material, which comprises dissolving theniter from said material by treatment with a solution which is saturated when cold or moderately Warm With niter and with soluble impurities of the niter-bear-v ing material, the temperature of said solu- -tion during the treatment o f said niter-bearing material therewith being considerably below the temperature at which the greater portion of said impurities is deposited out, whereby the resulting solution produced by said treatment contains, in addition to 'the niter content of said material, a relatively large amount of impurities, and cooling the solution so produced to obtain impure niter crystals; substantially as described.

ln testimony whereof l affix my signature.

.HARRSN STREETER @@E.

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